Urban Heat Islands
Urban Heat islands are created by the unique thermal properties of cities. This is a combination of high concentration of concrete, glass and other man made building materials and low incidence of trees and water bodies.
On an average day the temperature in a city will be higher than the surrounding countryside. On some days this temperature difference is as much as 10 degrees Centigrade. This “island” of warmer areas is called a heat island.
Due to high pollution in a city including elevated carbon fuels ( petrol & diesel) the ground level Ozone content in a city is very high. Ground level or tropospheric Ozone is different from the Ozone that exists high up in the earth’s atmosphere. Think of ground level Ozone as the bad Ozone and stratospheric Ozone as the good Ozone.
Temperature and Ozone are interrelated. High Ozone means higher temperature and vice versa.
Ground level or bad Ozone is formed when nitrogen oxide and volatile organic compounds react with sunlight. Nitrogen oxide is a by product of high temperature combustion created by automobiles and power plants. Volatile organic compounds include organic chemicals that evaporate easily like petrol and diesel.
Essentially, nitrogen oxide plus volatile organic compounds plus sunlight creates ground level ozone.
High ground level Ozone can affect our health in many ways such as :
- Irritation of the respiratory system causing coughing and wheezing.
- Reduces lung function including deep breathing and viciously.
- Aggravation of Asthma.
- Reduces photosynthesis in plants creating weaker crops.